AP photographers returned to more than a dozen of those locations in recent weeks, from Portland to Cleveland and Corpus Christi, Texas. Of the 20,000 photos in the archive, the AP selected those that focused on environmental issues, rather than the more general shots of everyday life in the 1970s.

Gary Miller / U.S. National Archives via AP; Julio Cortez / AP

An illegal dumping area off the New Jersey Turnpike, facing Manhattan across the Hudson River, and north of the land fill area of the proposed Liberty State Park, N.J., is seen in March 1973, and an image from the same vantage point in April 2012 shows the Jersey City and New York City skylines with the green area near Liberty State Park in Jersey City, N.J., in the foreground.

Will Blanche / U.S. National Archives via AP; Frank Franklin II / AP

Ongoing urban development and construction on lower Manhattan's West Side is seen just north of the World Trade Center, right, in New York in May 1973. The same site is seen in April 2012.

David Falconer / U.S. National Archives via AP; Don Ryan / AP

The Publisher's Paper Company in Oregon City, Ore., on the Willamette River is seen in April 1973 at left. Together with Crown-Zellerbach Corporation, this company led a campaign to clean up the river. The Publisher's Paper Company, now closed, is seen in April 2012, right.

David Falconer / U.S. National Archives via AP; Don Ryan / AP

An 'Out of Gas' sign is seen, left, at the gas station at the intersection of SW Jefferson and 18th St. in Portland, Ore., in June 1973, during the fuel shortage. Similar signs cropped up all over the Portland area during the fuel crisis. At right, a restaurant sign on the corner of 18th St. and Jefferson shown in Portland, Ore., with a public transportation stop in the background.

Left: This photo, taken between 1972 and 1977 and released by the U.S. National Archives, shows a truck moving through a residential neighborhood on Lovell Street, adjacent to Logan Airport in Boston. The street ends at the Wood Island Transit Station near construction on a building to be leased to the food preparation business for one of the airlines. Right: The residential neighborhood that was once there is gone.

Neighborhood youngsters play in the playground adjacent to Logan Airport at the end of Neptune Road in the East Boston neighborhood of Boston in May 1973, left, and the same site is seen in April 2012, right.